This invention relates to a piezo valve with a housing which has at least one controllable medium connection and in which is arranged a piezoelectric bending element that has a sealing region and which can be moved against an elastically raised counterforce in accordance with an applied control voltage and which in a first switch position without control voltage is lifted from the seat of the controllable medium connection and in a second switch position subject to the control voltage and supported by the pressure of the medium to be blocked rests sealingly on this seat.
Such arrangements are known, for example, from the DE-A1 34 00 645, EP-A1 191 011, EP-A1 46 431, DE-A1 25 11 752 and DE-U1 86 07 094.0. In all cases a piezoelectric bending element can be moved in a valve housing between a feed and discharge seat, whereby the medium outflow can be connected either to the feed side or to the discharge side. In so doing, it is necessary to hold the bending element alive in the switch position blocking the discharge seat, a feature that has the drawback that at raised operating temperatures the piezoelectric bending element is deformed permanently by the prolonged electric voltage application, a problem that can be explained by the corresponding properties of the piezo materials used. Therefore, one must always strive to hold the switch positions, where the bending position is alive, relatively short, at least at raised operating temperatures that deviate from room temperature, a procedure that limits the application range of such valve or signal converters and thus constitutes a drawback, since in all cases it must be ensured that the bending element has not deformed itself permanently so much in the voltage application time that upon removing the voltage there is no more switch back.
The object of the present invention is to avoid the aforementioned drawbacks of the known arrangements of the aforementioned kind and to design in particular such a valve that both switch positions can be maintained for an abitrary length of time even at raised operating temperatures, without the risk of the bending element being permanently deformed and thus hindered in its function.